1. Field of the Invention
The present invention relates to a control device for a rotating machine of an elevator, for controlling the rotating machine which drives a hoisting machine of the elevator or the like, without using a speed sensor.
2. Description of the Related Art
In a conventional control device for a rotating machine of an elevator, an inverter having no speed sensor is applied to the control of the elevator with a view to controlling the rotating machine without using a speed sensor (see, e.g., Patent Document 1: JP 3260070 A).
In another control device for a rotating machine of an elevator, an adaptive flux observer is used to estimate a rotational speed with a view to controlling the rotating machine (induction machine) without using a speed detector (see, e.g., Non-patent Document 1: Transactions on the Institute of Electric Engineers Japan (IEEJ)-Industry Applications Society I-55 (1998), “Stability Analysis of Adaptive Flux Observer of Induction Motor in Regenerative Operation.”).
In still another control device for a rotating machine, which controls the rotating machine (induction machine) without using a speed detector, with a view to preventing overcurrent stoppage of an elevator resulting from an increased load and enhancing the accuracy with which the elevator arrives on a floor, it is detected that an output current of an inverter has reached an overcurrent limit level lower than an overcurrent stoppage level, constant-speed control is performed at a speed at the time of the detection, and the same deceleration control as in the case of deceleration for a certain period of time is performed such that the same deceleration distance as in the case of deceleration according to a speed pattern is obtained when a riding car has reached a deceleration starting point (see, e.g., Patent Document 2: JP 05-017079 A).
However, the conventional arts have the following problems. In the conventional speed control device for the rotating machine disclosed in Patent Document 1, for example, the output of a slip frequency command is changed in accordance with the load of a car in an acceleration interval in which a frequency command for an inverter is in the process of reaching a predetermined value after the operation of the elevator has been started. However, the running curve of the elevator is held constant regardless of the load of the car in a deceleration interval in which the car is in the process of stopping after the frequency command for the inverter has reached the predetermined value.
In the conventional control device for the rotating machine disclosed in Patent Document 2, when the control is performed without using a speed detector, deteriorations in control stability and control performance are observed in a low-speed regenerative range. Therefore, a speed pattern according to which a maximum deceleration is reduced in advance so as to prevent the entrance into the low-speed regenerative range must be used. As a result, the time for deceleration is prolonged regardless of the live load of the car of the elevator, so there is caused a problem in that the moving time of the elevator is prolonged.
If the speed pattern with restricted deceleration is not used, the moving time of the elevator is not prolonged, but a problem such as a deterioration in riding comfort arises due to a decrease in stability resulting from the passage through the low-speed regenerative range. Further, in Non-patent Document 1, the observer needs to be separately designed with high stability.